But researchers at two Australian universities have developed an underwater robot that could help turn the tide in the ongoing struggle to save at-risk reefs. The briefcase-size submersible, dubbed LarvalBot, is designed to move autonomously along damaged sections of reef, seeding them with hundreds of thousands of microscopic baby corals.

“The reduced number of corals means we’ve lost the ability for coral to provide enough larvae to settle and restore these communities quickly,” said Peter Harrison, director of the Marine Ecology Research Centre at Southern Cross University and the leader of the coral restoration project. “The idea here is to use an automated technique that allows us to target delivery of the larvae into damaged reef systems and increase the efficiency that new coral communities can be generated.”

Harrison’s team recently tested LarvalBot at Vlasoff Reef, an outer part of the Great Barrier Reef along Australia’s northeastern coast. In the trial run, the submersible dispersed 100,000 baby specimens derived from corals that survived the bleaching event of 2016-17, which are believed to be especially tolerant of warmer ocean temperatures.

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Future versions of the bot should be able to disperse millions of baby corals in order to speed the regrowth of damaged reefs, Harrison said, adding that the team is also planning to test LarvalBot on a reef in the Philippines.

But the researchers will have to wait and see if the microscopic baby corals take hold.

“We can’t actually see the results of these experiments until we start to see juvenile corals grow — so, for at least six to nine months,” Harrison said. “What we’ll be doing now is monitoring the reef over the coming months.”

LarvalBot is based on another submersible robot known as RangerBot, which was designed not to deliver babies but to kill a coral-eating species of starfish. RangerBot was developed and built by Matthew Dunbabin, an engineering and robotics professor at Queensland University of Technology, who also reworked the RangerBot to carry the baby corals.

Harrison hopes to eventually develop a fleet of LarvalBots that would be used to repopulate reefs around the world, though he is unsure how much such a project would cost.

Mark Eakin, the College Park, Maryland-based coordinator of the National Oceanic and Atmospheric Administration's Coral Reef Watch program, called Harrison's project an "excellent idea" but questioned the effectiveness of underwater robots in tackling a global problem like coral loss.

“The area of coral reefs hit by significant mortality is about the size of the state of West Virginia,” Eakin said. “Now, imagine dividing the state of West Virginia across the entire Pacific Ocean. We need to be doing everything we can to protect coral reefs, but we have to keep in mind that this problem is absolutely huge compared to what these robots can do.”

“Even if this technology is scaled up, if we don’t deal with climate change, it won’t be enough,” he said. “It’s like coming up with a robot to replant trees after the devastating wildfires that just happened. It’s not addressing how to stop the wildfires in the first place.”